Shortly after being named the 2002 TR100 Innovator of the Year, Max Levchin left PayPal, the company he had cofounded, which he and his partners sold to eBay for more than $1.5 billion. About a year later, he founded Slide, a company that creates playful ways to showcase photos on home pages, blogs, and social-­networking websites like Facebook. Slide is currently one of the most ­popular services of its kind, allowing the images of more than 120 million users to swirl, revolve, fade, or “steam” into existence somewhere on Web.

Technology Review: If you were able to give your 26-year-old self any advice, what would you say?

Max Levchin: Don’t take the year off between companies.

TR: Why?

ML: It was probably the most miserable year of my life, between PayPal and Slide. If you start companies for fun, you find, unless you’re capable of truly relaxing and not thinking about new ideas and work, that it’s actually painful to take time off. If somebody told me, “You will go stir-crazy; you won’t be able to keep your mind off the markets; you’ll keep thinking about stuff, and it’ll be more pain than good,” I’m not sure I would have listened. But that was a year when I could have done some awesome work. Instead, I was really trying to relax, and that didn’t work out at all.

TR: Do you find greater fulfillment in producing rather than–

ML: Consuming? Absolutely. One of the interesting lessons I’ve learned is that you only value things when they’re scarce. It really extends all the way down to your personal life. And I think if you’re an entrepreneur, you’re an extreme scarcity fanatic. You’re fundamentally trying to find or create things that are scarce and arbitrage that. And so when you have ridiculous and, therefore, worthless amounts of time, you tend not to value it at all. When you work as hard as we do starting companies, you have three hours to sleep and four hours to take off during the weekend. Those are the best four hours you get. You’re still thinking about work, but you’re very thankful to have that time to ride a bike for a while.

TR: What’s your biggest challenge ahead?

ML: On a personal level, a CTO ultimately is still an engineer, which is what I am by training and by first love, and I still love engineering–you feel like you’re moving the needle with your own hand. Engineers are happiest when they feel like they’re contributing to a cause by doing something. And a lot about being a CEO is learning how to contribute to the cause less by your own hand and more by motivating others and feeling happy when they accomplish goals, sharing in their success and celebrating it and channeling it to others. That’s not a particularly engineering-type thing to do. My biggest challenge is that I’m still learning to delegate.

TR: Do you have any advice for this year’s members of the TR35?

ML: One piece of advice I sort of wish I had heard is “Do it again. Keep at it.” I had considered going off and studying theoretical math for a while, because that’s what I really wanted to do when I was younger, or going to join a more financially bent institution like a hedge fund or a VC. I played around with those ideas in my head and met with people who could give me advice, many of whom were very keen on recruiting me to do those kinds of tasks. And eventually I realized that if you’re cut out to be an entrepreneur, you’re not going to be particularly happy doing something else. You’re only kidding yourself into thinking something else might work. I wish someone had told me at the time of the TR event–

TR: To know thyself?

ML: Yeah, you’re exactly who you are; you’re going to start another company. The funny thing is that the one thing I was really into before, during, and after PayPal was math and number theory. I really wanted to do a PhD in number theory or cryptography. This may sound a little geeky, but if I had an infinite amount of time and ability to focus on things that aren’t business related, it’d be exactly what I’d want to do. One day during my year off, I got to talking with the person that I wanted to be my PhD advisor, who was at first quite keen on this idea. But eventually he said to me, “You know, you’re kidding yourself. You’re going to go start another company. Just deal with it.” And I said, “No, no, come on, Dan, I’m going to make it happen!” And he said, “Nah, you’re going to start another company.” And he was right.